A lawyer advising a group trying to save the Christ Church Cathedral says the Anglican Church's wish to demolish the building is irrelevant.
The group, Restore Christ Church Cathedral, has sought legal advice from the high-profile public law firm Chen Palmer.
One of the firm's lawyers, Nick Russell, says the Historic Places Trust has a statutory obligation to protect the cathedral as a heritage building and an archaeological site.
He says that overrules the wishes of the Church Property Trust, which owns the building.
Meanwhile, another group, the Great Christchurch Buildings Trust, has taken the fight to the High Court, seeking a ruling on whether the church's demolition plans breach an act of Parliament designed to protect the building.